One method that has always worked well for me is measuring the total square footage first, then adding a waste factor based on the room layout. For simple rectangular rooms, I usually allow around 8–10% extra. If the room has lots of corners, closets, or a diagonal/herringbone pattern, I increase it to 15–20% because there are more cuts and offcuts. It’s also worth ordering a little extra from the same batch in case you need future repairs or replacements. It’s much easier than trying to match the flooring later.